294 



CLASS ASCOMYCETEAE 



Fig. 95. Hemisphaeriales, Family Microthyriaceae. Asterina camelliae Syd. & 

 Butl. Perithecium and mycelium. (After Theissen and Sydow: Ann. Mycol, 15(6) :389- 

 491.) 



Family Polystomellaceae. Stromata with radial structure as in the 

 preceding, but external to the cuticle and arising from an internal myce- 

 lium ("hypostroma") from which emerge strands through the epidermis 

 at various points to give rise to the stromata. There are 39 genera of which 

 20 form very narrow perithecia which formerly led to their being placed 

 in the Hysteriales. Parmidaria (perhaps more correctly named Schneepia) 

 belongs here. Polystomella is the type genus of the family. 



Family Microthyriaceae. Stromata with radial structure, vegeta- 

 tive mycelium and stromata entirely superficial. There are 36 genera with 

 over 150 species; all but a few are leaf parasites. Here and there, on the 

 more or less reticulately arranged coarse brown vegetative mycelium 

 (whi(;h is lacking in a few genera), appear the almost lens-shaped stro- 

 mata. In each, under the radial centrally ostiolate cover, is a hymenium of 

 vertically standing asci intermingled with conspicuous or inconspicuous 

 (rarely lacking) paraphysis-like remnants of the stromatic tissues, which 

 in a few cases form a definite epithecium-like layer. The stromata are 

 mostly round but are in some cases laterally compressed. Among the 

 forms without vegetative mycelium is the genus Microthyrium in which 

 the stromata appear as little black superficial dots on the leaves or stems 

 of various plants. Asterina forms small round stromata and Lembosia linear 



